This Lead Award application proposes a major expansion and deepening of the research currently pursued on Alzheimer disease (AD) at the institution of the Senior Investigator (SI). It includes four research projects, one by the SI and three by junior investigators. Four pilot projects are also presented. They propose innovative research which may open novel approaches or lead to a breakthrough in AD research. Project 1 by the SI, is a systematic study of the heat shock protein (HSP) system, beta amyloid precursor protein (betaAPP) and of the ubiquitin system in the nervous system with the overall aim to establish the role of HSP and Ub systems in AD and to assess whether betaAPP is expressed as a HSP. Five sets of studies are proposed: 1) Response of HSP, betaAPP and Ub as well as the formation of Ub conjugates in neurons, astrocytes and microglial cells to heat shock and other stress conditions. 2) Effect of aging on these responses. 3) Role of HSP, betaAPP and Ub in the formation of neurofibrillary inclusions and dystrophic neurites. 4) Unidentified HSP which may play a role in AD. 5) Ub conjugates forming under normal and pathological conditions mimicking the cytoskeletal and neuritic alterations of AD. Project 2 deals with expression regulation of HSP, betaAPP and Ub in normal and experimental conditions as well as in AD and related disorders. The following questions are investigated: 1) Is expression regulation of HSP and Ub different in neurons, astrocytes and microglia? 2) How is expression of these proteins and of betaAPP regulated in experimental models reproducing lesions similar to those of AD? 3) Is expression of these proteins altered in AD, Pick's disease and Progressive Supranuclear Palsy? Project 3 focuses on amyloid formation. It evaluates expression of betaAPP in the non-neuronal cells surrounding senile plaques (SP) using intact tissue and culture systems. Processing of betaAPP will be analyzed in culture systems of astrocytes and microglial cells exposed to various forms of purified betaAPP. Project 4 will answer the following questions: 1) Are straight filaments (SF) and paired helical filaments (PHF) in continuity with each other and with neurofilaments and microtubules? 2) Are Ub conjugates present in dystrophic neurites of SP located in SF and PHF only, or also in membranous structures? 3) Which cells are involved in the early stages of amyloid deposition in SP and vessels? 4) Is tubulin present in PHF? The four Pilot Projects deal with: a) a novel method of solubilization of PHF; b) analysis of cerebrospinal fluid proteases involved in cleavage of betaAPP; c) substraction hybridization as a technique to identify putative AD genes on chromosome 21; d) an attempt to produce PHF experimentally. Altogether the projects proposed in this LEAD Award application strengthen and expand in a major way research on AD carried out under the SI's overall leadership. They will add novel areas of research which take advantage of new technologies, they will foster further development of junior investigators already committed to research in AD and will introduce new talented investigators to this field of research.